The technology described in this application is basically concerned with the optimization of traffic routing of packet data traffic of a packet service, e.g. of packet data traffic of GPRS (General Packet Radio Service). More specifically, the application is directed towards the problem of “local breakout” in the event of roaming. As it is known, a terminal that subscribes to a given communication network (e.g. a wireless terminal that subscribes to a mobile communication network) may often not only attach to the network it subscribes to, which is also referred to as the home network, but also to other networks than the home network, which are then referred to as visited networks. The possibility of attaching to a visited network is referred to as roaming.
One possibility for the handling of packet data traffic in a visited network is such that the traffic from visiting terminals is tunneled to the home network of the visiting terminal, for processing there. However, such a routing of packet data traffic between networks can lead to considerable delays in the packet data communication, which can in turn lead to unsatisfactory performance at the communication end-points. Delays could be reduced by handling packet data traffic locally in the visited network, which is also referred to as “local breakout”. Local breakout will not only reduce delay, but can also improve the transport efficiency.
As a mechanism that can also be used for performing local breakout, GPRS describes the concept of APN (Access Point Name). This will be explained with reference to FIG. 7.
In FIG. 7 reference numeral 70 describes a communications network in which the roaming wireless terminal 72 is visiting. The terminal 72 interacts with network 70 via an access network (e.g. GERAN (GSM EDGE Radio Access Network)), indicated by 71 in FIG. 7. The access network 71 (which can e.g. comprise base stations and associated control elements, such as Base Station Controllers, Radio Network Controllers, etc.) interacts with an SGSN (Serving GPRS Support Node) 701. The visited network furthermore comprises a GGSN (Gateway GPRS Support Node) 702 and a DNS (Domain Name System) 703. FIG. 7 furthermore shows a GRX (GPRS Roaming Exchange) 73 comprising a DNS 730, and the home network 74 of terminal 72, which comprises a GGSN 740 and a DNS 741.
In accordance with the APN concept, the SGSN 701 is capable of obtaining the address of a GGSN for processing the packet data traffic of the terminal 72. More specifically, the APN is translated into an IP (Internet Protocol) address of a given GGSN using the DNS. The APN has a format comprising a so-called “network ID” that points to an access point within the network, and a so-called “operator ID” that points to a network in terms of an identity of the respective operator. As a consequence, the “operator ID” is generically speaking a network identifier, as it identifies a network. The basic structure of the APN is                <network ID>.<operator ID>. gprs.        
The visited SGSN 701 interrogates the DNS 703 (see arrow 704), in order to translate an APN into a GGSN IP address. If the DNS 703 in the visited network 70 is unable to provide an IP address for the APN, e.g. because the APN is not supported by the visited network, it turns to the DNS server 730 in the GPX 73. The DNS 730 possibly provides the desired GGSN IP address, or returns a failure notice in which case the DNS 703 queries the DNS 741 of the terminal's home network 74.
Once the GGSN IP address is available at the SGSN 701, it can appropriately perform a PDP (Packet Data Protocol) context towards the indicated GGSN. It sends the “network ID” of the APN, but not the APN “operator ID” to the indicated GGSN. In the example of FIG. 7, the SGSN 701 can therefore perform a PDP context activation towards the GGSN 702 in the visited network 70, which amounts to a local breakout, or towards the GGSN 740 in the home network 74, depending on the APN.
The APN “network ID” can be supplied by the terminal 72, by the network (via a subscription record), or can be a default parameter chosen by the SGSN 701. The APN “operator ID” may be supplied by the terminal 72 as an option, where only the visited network 70 or the home network 74 are possible. If no “operator ID” is supplied, then first the visited network 70 is tried then the home network. A further feature of the APN mechanism is the “VPLMN address allowed” field, which can be set to yes or no. VPLMN stands for visited Public Land Mobile Network and thereby refers to e.g. the visited network 70. With this mechanism the home network 74 can disallow APNs to a visited network. The value of “VPLMN address allowed” is part of the subscription record.
The problem with the APN mechanism is that it does not provide an efficient way to control the packet data traffic. If a single APN is used in the terminal 73, then all traffic must go via the home GGSN 740 or all traffic must go via the local GGSN 702 in the visited network 70. Since the operator of the home network 74 typically desires to have control over at least some of the traffic, this would imply that all traffic is tunneled to the home network 74. If multiple APNs are used in the terminal then it would be possible to separate the traffic into the APNs based on the service and let a part of the traffic go locally in the visited network, and let another part of the traffic go via the home network. However, this requires the configuration of a multiple APN in the terminal on a per service basis and a mapping of applications to a respective APN. A consequence of this is that each service in the terminal 72 will use a separate PDP context, and hence a separate IP address. This leads to complexity in the terminal configuration.